In a future mobile communication system, introduction of a network self-optimization mechanism is desirable for decreased manual participation in network planning, operation and maintenance and automatic optimization of parameters by a network from a statistic to thereby lower deployment and operation costs of the network. In order to lower operation and maintenance costs of the network, it is desirable to adopt a method for the network to configure a User Equipment (UE) for reporting to thereby lower an effort of manual drive-tests, which is referred to as a Minimization of Drive-Tests (MDT) scheme. On the other hand, it is also desirable to obtain through MDT radio measurement information of an area unreachable to normal drive-tests.
MDT is divided, depending on how to report an MDT result, into immediate MDT and logged MDT particularly as follows:
In immediate MDT, a user equipment performs MDT measurement and reporting in a connected status. A Radio Resource Management (RRM) measurement mechanism is reused to make a report to a base station/a Radio Network Controller (eNB/RNC) once a reporting condition is satisfied.
In logged MDT, a UE performs MDT measurement in an idle status and makes a report in a subsequent connected status. Once a configured trigger condition is satisfied, a measurement result will be obtained and logged and reported to an eNB/RNC on a subsequent appropriate occasion.
MDT measurement configuration can be categorized into cell-based MDT measurement configuration and UE-based MDT measurement configuration. FIG. 1 is a schematic diagram of transporting UE-based MDT measurement configuration parameters. A Mobility Management Entity (MME) can obtain UE-related MDT measurement configuration parameters (immediate MDT or logged MDT measurement configuration parameters) from a Home Subscriber Server (HSS). The MDT measurement configuration parameters include a measurement content, a report object and other information and also configuration policy information including a set of International Mobile Subscriber identities (IMSIs)/International Mobile Equipment Identities (IMEIs) and also possibly information on area scope of MDT measurement, Tracking Area (TA) or cell list information. The MME transmits the MDT measurement configuration parameters to a corresponding UE according to the configuration policy information.
At present a signaling flow of UE-based MDT measurement configuration is as illustrated in FIG. 2. In an Attach procedure of the UE, the HSS determines the UE to perform MDT measurement from a stored list of IMSIs/IMEIs for MDT measurement and transmits the MDT measurement configuration parameters to the MME to which the UE is attached, and subsequently if the MME determines that the UE resides in an area scope of MDT measurement according to the configuration policy information, then the MME has the MDT measurement configuration parameters carried in a initial context setup request message and transmits the message to the eNB, and if the eNB determines upon reception of the message that the message carries logged MDT measurement configuration parameters, then the eNB transmits the measurement configuration parameters to the UE in a piece of new Radio Resource Control (RRC) signaling; or if the eNB determines that the message carries immediate MDT measurement configuration parameters, then the eNB transmits the measurement configuration parameters to the UE in an RRC connection reconfiguration message.
The inventors have identified during making of the invention the following technical problems in the prior art:
For the immediate MDT configuration mechanism with the MDT measurement configuration parameters including the IMSIs/IMEIs and the cell list, in an initial access procedure of the UE, if a serving cell of the UE is absent in the cell list of the MDT measurement configuration parameters, then the MME will not transmit the MDT measurement configuration parameters to the current eNB. Thereafter the UE is subjected to an intra-eNB handover and a target cell after the handover is in the cell list, but the MME does not participate the intra-eNB handover, so the MME is unaware of the change to the serving cell of the UE and further will not know the entry of the UE into the MDT measurement cell range, meaning that the MME can not transmit the MDT measurement configuration parameters to the currently serving eNB of the UE so that the UE can not perform MDT measurement as necessary.